Transulnar access in patients with ipsilateral radial artery occlusion undergoing coronary angiography or angioplasty: Rationale and design of the ULNART study

BACKGROUND: In patients with radial artery occlusion (RAO), contralateral transradial access (TRA) may be infeasible or strategically undesirable. Transulnar access (TUA) ipsilateral to RAO is anatomically plausible; however, contemporary evidence on vascular safety and hand function is limited and methodologically heterogeneous. ULNART is a prospective, multicenter cohort designed to evaluate the short- and long-term safety and functional outcomes of TUA ipsilateral to RAO using standardized imaging, quantitative testing, and patient-reported outcome measures (PROMs). METHODS: Adults with documented RAO undergoing elective invasive coronary angiography or percutaneous coronary intervention (PCI) are enrolled when contralateral TRA is not feasible or when preservation of the contralateral radial artery is clinically desirable. Baseline assessment includes color duplex ultrasonography (CDUS) to confirm RAO and evaluate ulnar artery suitability. A focused bilateral neurologic examination in the ulnar nerve distribution is performed to identify pre-existing motor or sensory deficits. Bilateral quantitative assessment of hand function and sensation includes handgrip strength, key pinch strength, and tactile thresholds, measured using validated instruments (JAMAR dynamometer, pinch gauge, and WEST monofilaments). Patient-reported outcomes are collected using the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) and Cold Intolerance Symptom Severity (CISS) questionnaires. Procedures are performed via TUA ipsilateral to RAO with per-protocol anticoagulation and hemostasis is achieved with a compression device adapted at the access-site point. Patent hemostasis is initially confirmed by CDUS and then monitored by plethysmography on the fifth digit. Follow-up assessments, including CDUS, neurologic examination, and bilateral functional testing, are conducted within 24 h after hemostatic band removal and at 30 and 180 days. The primary endpoint is a composite of serious access-related vascular and clinical neuromuscular complications at 30 days. Secondary endpoints include access-site crossover rate, early (≤24 h) and delayed (6-month) access-related complications, and longitudinal changes in handgrip strength, key pinch strength, tactile sensibility, and PROMs. The study targets 127 participants, providing a two-sided 95% confidence interval with a ± 4% half-width around an expected 5% primary event rate. CONCLUSIONS: ULNART will provide prospective evidence on the safety of TUA ipsilateral to RAO and its effect on hand function. The findings are intended to guide access selection when TRA is unavailable, inform patient counseling, and support follow-up strategies in this population.